How the home of a pioneering Microsoft programmer–turned–climate advocate could lead the way in energy efficiency.

After 23 years living in their expansive Volunteer Park home—a drafty old Tudor built in the early 1900s—and with two children leaving for college before too long, Jabe Blumenthal and his wife, Julie Edsforth, decided to build something new. “Which is somewhat a self-indulgent thing to do,” admits Blumenthal. “So we wanted to make sure it advances the things we care about.”

What Jabe Blumenthal cares about is the environment. After a successful career with Microsoft in the ’80s and ’90s, where he codesigned Excel, Blumenthal spent the next 16 years involved in climate politics and advocacy. His search for ultra-low-energy consumption led him to research passive homes, a building standard that prioritizes efficiency in heating and cooling.

“What it comes down to is reduced thermal bridging,” explains lead designer Prentis Hale of Shed Architecture and Design, which is a fancy way of saying the home’s interior temperature is on lockdown. Exterior insulation, tight seals where walls and ceilings meet, and strategically placed triple-pane windows work together for maximum thermal control, designed, in this case, through a software package that quantifies energy efficiency down to the square foot.

Unlike Blumenthal’s old Tudor house, which needed near constant heat to keep things at a comfortable 68 degrees since air just kept escaping, the new house is naturally more uniform in temperature. “The optimal passive home is actually a basic rectangle,” says Hale. But neither designer nor client was about to stick a giant box on the stately east-facing hills of Madrona. The house’s interlocking rectangles, laid out like cells of an Excel spreadsheet, take advantage of 180-degree views, while the mocha-colored wood paneling adds an organic touch to the otherwise unnatural angles.

Inside, the triple-pane windows of the lofty central room capture heat and a stunning view of Lake Washington. With a 9.75 kilowatt solar setup, energy-efficient appliances, and a high-tech C02 heat pump that’s so new it’s being studied by Washington State University, Blumenthal is flirting with net-positive energy usage, and that’s with an electric car charging every night and a heat-storing sauna.

There’s a reason passive homes like these aren’t popping up around the city as a new residential building standard, and that is of course cost. And not just because of the Madrona location. “There are relatively few people who know how to build like this,” says Blumenthal. “Somebody has to start building the first 10 or 20 of these to drive the cost down.”

But the results are palpable, if not a little strange sometimes. On a recent holiday visit, Blumenthal’s mother showed up with unbaked cinnamon rolls. “She asked me where the warm spot in the house was so she could put them somewhere to rise,” he remembers. “And I told her, when it says 68 degrees in here, everything is 68.”